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cylonlover writes "OK, first things first – stop picturing a car with solar panels connected to its engine. What Missouri-based inventors Matt Bellue and Ben Cooper are working on is something a little different than that. They want to take an internal combustion engine, and run it on water and solar-heated oil instead of gasoline. That engine could then be hooked up to a generator, to provide clean electricity. While that may sound a little iffy to some, Bellue and Cooper have already built a small-scale prototype."

Separating oil and water which have been mixed at such a fine level doesn't seem the easiest. While I know it can be done, can it be done in such a manner to maintain any of the heat energy which remains? Or does one just accept that energy as lost?

seems stupid, though: we have good heat-exchangers that don't require mixing the two fluids. Just coiled metal pipes (add fins if needed) would do the trick.

We've been building liquid sodium/water exchangers for nuke plants for years. There is zero reason to mix the fluids and then add a separator (which is a real pain in the ass given the oil is in a closed cycle.)

seems stupid, though: we have good heat-exchangers that don't require mixing the two fluids. Just coiled metal pipes (add fins if needed) would do the trick.

The point of mixing the fluids is that you cannot otherwise impart enough heat to flash boil the water.Not to mention that it's really hard to do what you're suggesting inside the cylinder

There is zero reason to mix the fluids and then add a separator (which is a real pain in the ass given the oil is in a closed cycle.)

The whole point of their technique is that they create steam inside the strongest part of an engine.As it turns out, oil and water will try to separate on their own, which makes this a less than complicated issue.

Not really. How can you make the transfer of heat more efficient between two liquids by separating them? Especially when one of them is being turned into a gas, which would act as an insulator between the separating surface and the rest of the liquid.

can you not otherwise impart enough heat to flash boil the water? Why not a big metallic thermal load, made out of recycled popcans?

I believe the trick here is that because you're injecting the "fuel" (liquid water) and injecting the heat source you are able to very precisely control the timing of the engine as well as control the steam's wave front. If you had a static heat source inside the engine there's not only the question of how you deliver heat to that, but also how you control triggering of the p

seems stupid, though: we have good heat-exchangers that don't require mixing the two fluids. Just coiled metal pipes (add fins if needed) would do the trick.

The point of mixing the fluids is that you cannot otherwise impart enough heat to flash boil the water.Not to mention that it's really hard to do what you're suggesting inside the cylinder

That is just not true. Look at a steam catapult, or a pressure cooker, or even a classic rail locomotive. You just need a boiler under some pressure.

There is zero reason to mix the fluids and then add a separator (which is a real pain in the ass given the oil is in a closed cycle.)

The whole point of their technique is that they create steam inside the strongest part of an engine.As it turns out, oil and water will try to separate on their own, which makes this a less than complicated issue.

"Trying to separate" is a lot different from actually separating. Heat a pan of oil to 400 degrees in your kitchen, now dribble water drops onto the oil for a minute or two. Notice how greasy your kitchen tops are getting? Heat transfer == physical motion in liquids == oil in your steam.

How do you plan to separate the stream/oil droplet mixture? Do simple experiment: shake a pint of cooking oil and water together. How long did they take to separate back out? 1 hour to get to 95%? Now try it at high temperatures: you are talking days unless you have a serious refrigeration unit in your engine.

How do you plan to separate the stream/oil droplet mixture? Do simple experiment: shake a pint of cooking oil and water together. How long did they take to separate back out? 1 hour to get to 95%? Now try it at high temperatures: you are talking days unless you have a serious refrigeration unit in your engine.

Oil and water separation is a solved problem.

"How" depends on the volume of emulsion, the available space and power.Maybe they'll use a centrifuge. Maybe electrostatic separation.Maybe they'll heat the oil with a peltier and use the cool side as "a serious refrigeration unit".

I'm not an engineer and even if I was, TFA doesn't provide enough information to 100% answer your question.But like I said, it's a solved problem.

Maybe they'll use a centrifuge. Maybe electrostatic separation.Maybe they'll heat the oil with a peltier and use the cool side as "a serious refrigeration unit".

All of those take energy that would sap the efficiency of the system. I'd probably go with a large condensation box that has baffles in it like a septic tank to keep disturbances down. As the liquids cool and travel through/around the baffles, they're slowed and turbulence is minimized.

You might not need a 100% efficient separation system to make it work.

Still, I don't see it being more efficient at this point than traditional steam engines and turbines.

You would probably use an electrocoalescer. It's very commonly used in the oil industry, where water and oil is mixed into an emulsion in the wellhead choke valve. (An electrocoalescer is a fancy name for a tank with an applied electric field, either AC or DC, of around 10-100 kV/m.)

Since they have to condense the water back out to run it through the engine once again, presumably it shouldn't be that hard. At some point you'll get it all back into a reservoir of liquid water with oil mixed in. Skim the oil off the top and feed the engine with water pumped from the bottom.

dom

"Presumably?" Have you ever cooked in a kitchen or worked with machinery that has an oil/water interface?

If the injectors can handle both oil and water, and you have a pressure release valve in your hot oil reservoir, I see no reason why partial mixing would be a problem.
You would get a build up of grease and such, but engines do that anyway.

In my early years I did a bit of basic motorcar repairing. Nothing ambitious.One obvious issue for all, was that whenever a watercooled motor got a leak between oil and water, the result was *mayonnaise*, a compound of oil and water which DEFINITELY won't separate "on their own" --just try it: get a mayonnaise cup, and watch it separating;-)At that time basically the motor was dead.Now, I understand there may be ways to try separating. Maybe.

There is one, oil/steam mixtures are ferociously combustable, and would easily allow one to burn diesel or even used engine oil in an spark ignitioned internal combustion engine; but even that seems a little like a Rube Goldgerg machine to me. There are people who are working on converting the Detroit Diesel Series 71 [wikipedia.org] engines to steam operation, a two cycle diesel would seem fairly easy to convert.

We've been building liquid sodium/water exchangers for nuke plants for years.

Yes, and the Russians may get it right this time with the reactor they have under construction. I'm a bit disgusted that you are trivilising it as if it is a common thing and as if they are not major maintainance problems and pretending you know what you are writing about. The French had to rebuild such systems from scratch several times for Superphoenix and their final result is the current state of the art.

If you use a small amount of oil to flash a relatively large amount of water you would get better efficiency, but you'd need to heat the oil to higher temperatures which brings its own problems. Also separating oil and water is easy, seeing as they don't actually mix.

Also separating oil and water is easy, seeing as they don't actually mix.

The oil is assuredly atomized to increase surface area and heat transfer, seeing as the timing of such an engine depends on precise (and rapid) water phase change. Much like a diesel engine you're relying on very precise injection timing and predictably fast burning/expansion.

A oil/water mixture composed of such tiny droplets is not trivial to separate.

But, how much separation do you really need? From RTFA, I don't think that having oil mixed with the injected water would cause any problems. It would decrease the efficiency, but I would imagine that you could get the oil concentration below 5% pretty easily. And, at those concentrations it seems that the effect on efficiency would probably be negligible.

Separating oil and water which have been mixed at such a fine level doesn't seem the easiest. While I know it can be done, can it be done in such a manner to maintain any of the heat energy which remains? Or does one just accept that energy as lost?

Wouldn't you just cool it below the vapor temperature of the oil and/or water then separate it as liquids? A lot of the will be lost, but not all. Some of the energy can be recaptured by preheating the liquid water and oil.

They're going to have to cool and return at least the water back to liquid state anyway before it can be injected again for the next cycle.

Yes, they have reinvented the steam engine.In this case, literally: it runs on stream. (As opposed to many more modern heat engines, which usually use other working fluids).

The innovation seems to be that they have separated the heat absorption from the expansion of the working fluid.

If the best they can do is 15%, it will not be competitive with photovoltaic, ever. This needs tracking and mirrors, and that kind of moving parts just can't beat the production efficiencies of silicon solar cells.

The only reason this MIGHT compete with solar is the ability to store the thermal energy overnight. Storing heat (as molten salt or hot oil) is easier and less expensive than batteries to store electricity.

That said, this seems like an awfully inefficient way to go about it and there are already solar thermal plants of different varieties that are commercial-scale, more efficient and less Rube Goldberg-y. I can't see any sensible way to get the oil out of the cylinder without high pressure purge, and if the

Not really. You could turn photovoltaic power into heat energy (with a resistor), and use it to heat up a molten salt, but the efficiency losses and the cost of turning this back into electrical power is absurd.

According to TFA 15% is the same efficiency as photovoltaic but the cost of the system is supposed to be 1/3 of equiv photovoltaic.

Yes, they said that, but they're wrong. No possible way it can get down to 1/3 the cost of photovoltaic panels. I frankly doubt if they can make it as low as twice times the cost of photovoltaic.

On a large enough scale, I think a Brayton engine might make it cheaper than photovoltaic, but part of that is because of the high efficiencies, and the other part the economy of scale of large turbines. I doubt a piston engine can be that cheap, not operating at these temperatures.

Interesting that the OP got instantly modded down. Suppose the article was about a new computer language and the article described it as a compiler when it really was an interpreter. Bullshit would be called immediately. Same level of error, different tech.

While the engine may ideally just vaporize the water with hot oil, the reactions involved would eventually degrade the oil. Additionally, the separations processes are often 50% of the whole system's energy requirements, I just wouldn't see the viability of such a system. Now a heat exchanger for hot oil/water vaporization would wake a lot more sense, but it seems they want to generate a funding buzz with an internal engine spin.

This could probably happen on the way back to the solar collector as the oil is heated back up, then you would just have to condense the steam back into water. Most of the steam would likely just exhaust on its own, but what's trapped in the oil would come out once it's reheated.

It's not being burned, it's only being used as a heat carrier. Seems to me it would be more efficient to just heat the water directly, and use it in a steam turbine. What am I missing here?

The hydraulics. I can't be bothered to crack open a steam table at this time of day, but a substantial sized tank of stored 500F water is going to be ridiculously thick walled and heavy... 500F oil can be more or less unpressurized.

Reading the article I'm not sure what "oil" they're using. Cheap canola oil isn't going to like 500F however asphalt isn't going to like being piped around at room temp.

The journalist articles don't detail it, but stereotypically there is a huge insulated front end tank being heated by panels so you can run the engine at midnight. Usually its a couple orders of magnitude cheaper to redesign the system to not require operation at midnight, but thats a higher level system failure.

Usually its a couple orders of magnitude cheaper to redesign the system to not require operation at midnight, but thats a higher level system failure.

In the near term, for residential power production I think the best method is to use the grid for "storage". The system would need to be able to gracefully shut down and restart without human intervention, though. PV handles that very gracefully and naturally, this would have to be engineered for it.

It's the flash heating of the water into steam in the cylinder which creates the pressure to drive the piston. Using oil as the heat carrier is simply how they've chosen to concentrate as much heat as possible into a small volume with high surface area as a liquid. The only other way to achieve this would be to heat the edges of the cylinder to much higher temperatures (as they're solid and have low surface area so they don't transfer heat as well) which would likely damage them and reduce efficiency.

... that Slashdot had been finally invaded by the 'run your ICE-powered device on water' fraudsters who are all over the car forums on the web now. Thankful to find its just a bad description of using steam expansion as part of a power stroke (BMW tested the same theory using steam generated or augmented by the engines cooling system a few years back, although it worked for them they couldnt get the costs of it to be viable)

For the record before anyone does start talking about vehicle water injection, i

I thought I had seen some proposals for water injection where the water was only injected during full-power operation, where it would help keep the combustion chamber cool, and boiling the water would put more combustion energy into mechanical work instead of just heat. I agree that using it full-time would have its drawbacks.

It's somewhat commonly used with diesels, you inject it only when exhaust gas temperatures are high. its function is to reduce temperatures but it also gives you a power boost under maximum load conditions because the water changes state -- which is why it's so effective at removing heat. you can build a poor man's system with a pump and nozzles from AEM for about three hundred bucks, and a set-point controller like the Auber Instruments 1812, 1813 etc for about five bucks. They sell the controllers as 1/8

Water injection dates back to the 1920s. It was used because the technology of the day could not use high compression ratios without detonation. Modern technology overcomes detonation by attention to fuel, gas flow, thermal design and ignition timing. Water injection is obsolete.

It's still used in some crazy high performance engines. Both the Subaru Impreza and the Ford Focus in WRC used water injection. Can't get results for newer rally cars, but I don't think WRC teams put their current engine specs up on the internet. Those engines typically last around 100 hours, though.

I should have said that I meant automobile use - and specifically in reciprocating cylinder engines. The use of water injection on both piston and jet engines has proven benefits, however water injection kit is often sold nowadays under dishonest premises such as calling it 'water fuelling' and claiming notable reductions in petrol or diesel consumption. If it was marketed as a protective measure to prevent overheating I'd have fewer objections to the tactic, despite my reservations about retrofitting such

Most people think of "solar" or "wind" as renewable, but in fact, burning straw pellets could also work very well as a heat source and be carbon neutral (renewable). The nice thing about an engine like this is that any form of heat could drive it. Separating combustion from from the pressures in the engine also will eliminate NOx and other pollutants. So even if the solar part doesn't work out (or at night), this idea still has potential for carbon-neutral energy from just about any heat source that can heat up the oil.

First, while removing the boiler from the whole "steam plant" equation really does help the safety side of things, you have to be VERY VERY SURE that your separator removes ALL the water from your exhaust. Why? Because if you have even a tiny bit of water in your oil tank, and your heat it to 700F, it's going to boil and expand... and suddenly your low-pressure oil reservoir systems just turned into a really weak boiler full of oil that's hot enough to burst into flames. Instead of venting superheated invisible steam that can strip flesh from bones in seconds, you're going to be spurting oil around at temperatures that cause spontaneous combustion when meeting atmospheric oxygen. Not sure if that's really a step up.

Second, while oil and water don't mix, they do tend to form a really annoying to work with mayonnaise-like suspension of oil globules in water when mixed together really well. This takes a long time - or a lot of energy - to completely split apart.

Third, in addition to the previous problems with separating mayonnaise, heat dissipation will be an issue. Internal combustion engines carry a LOT of their waste heat away with exhaust, but in a closed-loop system like the one they're proposing here you need to remove the 85% of the energy you don't convert into work. Steamboats traditionally do this with a condenser that sits in the water, but if you're not near a large body of water, well... let's just say your condensing apparatus is going to be a huge, complicated, and difficult to work with because even if you don't have a high-pressure steam BOILER you're still going to have a high-pressure steam CONDENSER.

You could, of course, run the oil at a cooler temperature... but that drastically cuts back on your efficiency, because your power depends on having a lot of pressure inside the cylinder, and that pressure comes from the steam, and the pressure of the steam depends on the temperature... well, you get the idea. Basic thermodynamics.

So anyway. It's a cute idea, but unless they've got some really amazing tricks to solve the glaring technical fiddly parts I don't think it's going to get very far. I hope I'm wrong... but I don't think I am.

in a closed-loop system like the one they're proposing here you need to remove the 85% of the energy you don't convert into work

Why? It seems to me that in a system like this one the ideal temperature for the injected water would be just below the boiling point. Retaining heat in the water would reduce the amount of energy you need to inject in the form of hot oil for the same power stroke. The ratio and amount of oil and water to be injected will be highly dependent upon the temperatures of both, but with a computerized control system that doesn't seem like it would be a problem.

I should think the water won't last long in the oil as its being heated to 700 degrees, the watter should boill off and be recoverable with a condensor. This is assuming that you would want a closed circuit for the water.

If the plant isn't efficient as per "energy out" / "energy in" it could still be efficient as per "total energy out lifetime" / "total cost in dollars lifetime".

I should think the water won't last long in the oil as its being heated to 700 degrees, the watter should boill off and be recoverable with a condensor.

Only if the water is still steam when it exits the expansion chamber -- which should be easy enough to achieve by balancing the amount of oil and water injected, taking the temperatures of both into consideration.

When I first read this, I thought it was heating the engine block and then injecting water that flashes to stream, driving the power stroke. (So basically a two cycle engine - when the piston is at the top of the cylinder, water is injected, it flashes to steam, that drives the piston down, and when the piston comes back up on the second stroke, an exhaust valve allows the steam to escape. The exhaust valve closes at the top of the stroke, and the process is repeated.

Technical problems aside, there is no way the powers that be in the US will let any technology like this come to production. Our congress critters are heavily invested in OIL. They will only invest in clean energy that will certainly fail. They may invest research money into this, but only to find a way to make it fail. It has happened time and time again.

Except that natural gas is rapidly becoming a dominant player in the US, so you're completely full of shit.

This is not a combustion engine, at all. It's an "insert water with hot oil, use generated steam to drive engine, separate back oil and water to reuse" engine.

The potential efficiency is interesting, and the reduction of generated hydrocarbons compared to a normal motor of the awkwardness of creating and handling lead-acid batteries or other awkward electrical energy storage is also interesting. The difficulty of doing reliable water and oil separation for long periods, at low cost and with low power cost,

The difficulty of doing reliable water and oil separation for long periods, at low cost and with low power cost

Perhaps not so difficult if the water is still steam when it exits the expansion chamber. Then you'd be separating liquid oil from gaseous water (which would then have to be condensed). So the energy cost would essentially just be a bit more waste heat than is absolutely necessary. If you could separate them effectively while liquid you could try to tune the water/oil ratio so that the water flashes to steam but then cools back to just below the boiling point as it expands.

I quoted the article heading, and as you claim samzenpus claimed exactly that in the article heading. you obviously neither read my quote nor the article heading, or you did not understand it. I repeat: no he did not claim that.

A quick review of the Wankel engine also shows that this technology might be better applied there. The engine destroying accidental misfires known to some Wankel designes would not occur, and the problems handling the spark plug or with lubrication also would not apply.

Interesting if it works.- How hot is this engine going to get (safety)?- Insulation? (as he says)- Capture of waste heat? Something like this [transpacenergy.com]?- How is solar energy transferred to oil? With parabolic trough [wikipedia.org]?- Energy loss due to vibration of one piston?- Breakdown of oil?- Any limit to length of pipe running through collector?

The Solar Energy Generating Systems power plants in the Mojave Desert have been using parabolic mirrors to generate electricity via solar heat for nearly 30 years now, using oil as the heat transfer fluid.

"The sunlight bounces off the mirrors and is directed to a central tube filled with synthetic oil, which heats to over 400 ÂC (750 ÂF). The reflected light focused at the central tube is 71 to 80 times more intense than the ordinary sunlight. The synthetic oil transfers its heat to water, which

The heat collector system used in the SEGS plant isn't high-pressure. The oil used in the collector pipes never boils so it is only at a few atmospheres pressure, just enough to keep it circulating. The 400 deg C oil passes through a heat exchanger in central locations at each collector "farm" to produce steam that drives a turbine and generates electricity. This vastly simplifies the piping structure and keeps costs down while maintaining decent efficiency in terms of heat capture versus the amount of elec

This format of a heat engine isn't "going" anywhere as it would work only on a stationary position where the sun loading could be high with steerable mirrors. You could use molten oil, water or any material you chose to act as a heat source for a heat expansion engine.

For mobile uses, it all comes down to kilocalories stored per kilogram. This solution "won't go anywhere" mobile.

At this stage in development, efficiency isn't a big deal , unless it can be proven early on that it will always be too horrible compared to alternatives...and that only counts if there are alternatives.
What is interesting/important is it's potential as (pointed out lots of times in the comments) a steam engine that avoids big boilers and has the same kick as an ICE since it uses the same mechanical layout. Any other heat-driven engines that can do the same? same kick, same overhead?
reading comments seem

People, ICE stands for Internal Combustion Engine. Just because it has cylinders, pistons and valves it does not make it an ICE. It is a closed cycle engine. All the fluids used can be recycled and only heat will be added to them, and the mechanical energy extracted from them. Much like nuclear power plants. But piston/value thingies are much less efficient than gas/steam turbines. The only "innovation" here is to use oil to store the heat of solar energy. Again there are many other "fluids" including molte

From the indiegogo [indiegogo.com] campaign (yes, the summary neglects to mention this is a bloody crowdfunded uni project):

Efficiency: Both steam turbines and Stirling engines are known to be quite efficient, typically falling around the 40% efficiency range. We won’t know exactly where our HydroICE technology will fall until testing is complete, but we’ll be able to reach at least 15% efficiency with projections falling closer to 30%.

Manufacturing and cost: Both steam turbines and stirling engines are extremely precise machines and as a result, we see that reflected in the high price that it costs to manufacture and purchase one. This makes them economically feasible only for large industrial scale applications.

Yep, Stirling engines are too precise to be economically feasible, but similarly precise gasoline engines are so cheap that even with extra modifications they'll be feasible... right.

Yeah I know the guy is trying to get at the wider temp fluctuations in cylinder and piston temp, unless you go uniflow which has whole nother kettle of fish, but its not really much of a problem.

See if you try to crank up the efficiency and power of a trad ICE, eventually you get all manner of predetonation (ping) and trouble keeping crankshaft loads low enough while not letting the valves float and it gets all technical very fast. With a stirling you just crank up the heat until you melt or deform the piston/cylinder. Its more easily understood so its easier to empathize so its "seems" harder, but actually ICE are way more difficult its just we can't talk in uneducated company about the actual challenges. Any moron can understand "it melted" so any moron thinks stirlings are more difficult because they can't even talk about ICE engine optimization.

A Stirling engine [wikipedia.org] is *not* what you find inside any typical car. A Stirling engine is an external combustion engine (the heat source is provided from outside the engine) rather than the internal combustion engines (Otto cycle [wikipedia.org] for gasoline cars and Diesel cycle [wikipedia.org] for diesel vehicles) typically used. A Stirling engine has neither fuel injectors nor carburators - as an external combustion engine, it doesn't need to get fuel into the cylinders.

I don't know about that. Stirling engines seem to be popular projects for people getting started with home machine shops. Their cost is a matter of production volume.

but similarly precise gasoline engines are so cheap

Right. Because they are high volume production items. But one must figure one's economics based upon the assumption that one will go into large scale production. Not scrounging a bunch of parts adapted from some other use. If this technology is to become viable, piston engines will be designed and built specifically for this purpose (or for Sti

"But one must figure one's economics based upon the assumption that one will go into large scale production."

That creates a chicken and egg scenerio. Unless you have some massive VC capital backing you then you need to be able to produce units at reasonable prices in small volumes at first. Or else your technology will be overpriced, nobody will buy it, and you will never survive large enough to reach 'large scale production'.

There are dozens of companies that make this mistake every day. If you don't have

Modern day robotics make precision a non-issue. And with Stirling engines you can use more ceramics in the hot section since it's not exposed to explosive forces or crazy high RPMs like a gas turbine. Plus we can use them for refrigerator compressors without any specialized refrigerant. What they don't presently have is rapid throttle response, much like a regular steam engine, and to get a lot of power, they need to be very large, which is not an issue for stationary applications.

Precisely. Stirling engines have their niche: they make almost no sound, and work well under slowly varying loads. They are used for power generation in many applications. They have also been used in submarines for extremely quiet operation, both by marine explorers like Cousteau and by some navies. There have even been efforts to use them in small airplanes, since their output increases with altitude, while ordinary engines have less output at high altitude. I don't think they've made them successful in ai

I just read TFA, and what is described is in no way a combustion engine. Nothing is combusted.

They seem to carefully avoid mentioning it, but most oils when preheated to 700 degrees F (holy cow) and atomized in air will burn pretty well. Probably the water addition is to prevent the cylinder walls from melting, or more likely prevent them from looking like a well seasoned cast iron pan (which would have serious issues WRT cylinder rings)

I just read TFA, and what is described is in no way a combustion engine. Nothing is combusted.

They seem to carefully avoid mentioning it, but most oils when preheated to 700 degrees F (holy cow) and atomized in air will burn pretty well.

Since they plan to recover and reuse all of the oil, they must be assuming a type of oil that won't burn at the temperatures used. The GP is right: according to the article there's no combustion in the process. The design is an unusual sort of steam engine.

Of course, this raises the question of why it's better than a more traditional solar-powered steam engine. It clearly avoids the need to deal with high-pressure steam anywhere except in the "combustion" chamber, and if it can work well in slightly m

They seem to carefully avoid mentioning it, but most oils when preheated to 700 degrees F (holy cow) and atomized in air will burn pretty well. Probably the water addition is to prevent the cylinder walls from melting, or more likely prevent them from looking like a well seasoned cast iron pan (which would have serious issues WRT cylinder rings)